It's Cinema 4D and the Octane Render plugin in Cinema 4D. So it's kinda hard to talk about the learning curve. 3D software in general is a bit technical and challenging to first get into, but of all the 3D software, Cinema 4D is the easiest in my opinion, and at one time or another I've used just about all of them.

Also depends on your prerequisite knowledge, like if you already have a strong understanding of digital imagery in general, you'd understand everything a lot faster.